Global Greenhouse Gases, Sea Level and Ocean Heat All Hit Records in 2025

Greenhouse gas concentrations, global sea level and ocean heat content all reached record highs in 2025, according to the 36th annual State of the Climate report released Monday by the Bulletin of the American Meteorological Society. The international review, published as a supplement to the journal, is based on contributions from 625 scientists in 60 countries.

The Numbers

The globally averaged CO2 level reached 425.6 ± 0.1 parts per million in 2025 — a 53 percent increase from the preindustrial level of roughly 278 ppm — while fossil fuel emissions hit a record 10.3 ± 0.5 petagrams of carbon per year, more than three times the rate of the 1960s. Global mean sea level reached a record high for the 14th consecutive year, about 111.2 millimeters above the 1993 satellite-era baseline, rising roughly 3.5 mm per year. Ocean heat content measured to 2,000 meters depth also reached its highest level on record, with about 87 percent of the ocean surface experiencing at least one marine heatwave during the year.

Heat and Storms

The 2025 global mean temperature ranked among the three highest years on record — and was the warmest year ever recorded without El Nino conditions. Europe reported its warmest year on record, while Russia, China, South Korea and Argentina each logged their second-warmest. All five major temperature datasets agree the last 11 years were the 11 warmest on record.

Storm activity ran above average: 97 named tropical cyclones were observed across both hemispheres against a 1991-2020 average of 87, with five reaching Category 5 intensity. Hurricane Melissa became one of the strongest Atlantic hurricanes on record with maximum winds of 190 mph (306 km/h) and a central pressure of 892 hPa, killing 95 people in Jamaica and causing at least $12.2 billion in damage.